In the majority of patients with aortic regurgitation, valve replacement results in reduction in left ventricular dilatation and improvement in ejection fraction. To determine the relation between serial changes in left ventricular diastolic dimension and simultaneous changes in ejection fraction, we studied 50 patients by both echocardiography and radionuclide angiography before operation and early (6-8 months) and late (3-7 years) after operation. During both early and late postoperative evaluations, changes in diastolic size correlated significantly with changes in ejection fraction (p less than .001). Late improvement in ejection fraction after the early study occurred only in those patients manifesting an increase in ejection fraction between the preoperative and early postoperative studies. These improvements occurred predominantly in patients with normal preoperative ejection fraction or patients with subnormal ejection fraction but with preserved exercise tolerance and only a brief duration (p less than 14 months) of preoperative left ventricular dysfunction.